Heavy metal catalysts for emulsion polymerization reactions



Patented lily 31, 1945 HEAVY METAL CATALYSTS FOB EMULSION POLYMEEIZATIONREACTIONS William D. Stewart and Benjamin M. G. Zwlcker, Akron, Ohio,assignors, by meme assignments, to The B. F. Goodrich Company,-Akron,Ohio, a corporation of New York No Drawing. Application October 13,1941, Serial No. 414,788

Claims.

This invention relates to the polymerization of unsaturated organiccompounds which are capahie of undergoing an addition polymerization toform high molecular weight linear polymers, and particularly to thepolymerization in the form oi an aqueous emulsion of a butadiene eitheralone or in admixture with a monomer copolymerizable therewith Theprincipal object of the invention is to provide a method for decreasingthe time required to efl'ect such polymerization reactions.

It has already been disclosed in the copending applications of WilliamD. Stewart, Serial Nos. 379,712 to 379,717 inclusive filed February 19,1941, that the time required to eflfect polymerization reactions can begreatly reduced 'by the use of heavy metal catalysts. The heavy metalcatalyst may be in the form of a simple ionizable heavy metal salt inwhich case extremely small amounts such as from .001% to .0l% by weightof catalyst based on the monomers are employed, the optimum amountdepending upon the particular metal used. The heavy metal catalyst mayalso be in the form or a heavy metal complex wherein the metal is unitedto another element by coordinated covalences rather than by primaryvalences. These heavy metal complexes, called redox systems because oftheir property of catalyzing oxidation-reduction reactions, may containheavy metals such as copper. cobalt, iron, or nickel associated withcomplex-dorming compounds such as pyrophosphates, aliphatic carboxylicacids, bydroxy-substituted aliphatic m ercaptans, aliphatic polyhydroxycompounds or sterols. Heavy metal complexes may be employed inconsiderably higher proportions than simple heavy metal salts since theheavy metal is present in a practically unionized form. Amounts between.1% and 1% by weight of the heavy metal complexes based on the monomerspresent are in general suitable.

The term heavy metal is used herein to signify metals which have adensity greater than'iour. an atomic weight greater than forty and a lowat mic volume (ratio of atomic weight to density) and consequentlyappear at the minimum points above an atomic weight of forty on LotharMeyer's atomic volume curve. (See Ephraim "Textbook of InorganicChemistry" page 30 or Cavn and Lander "Systematic Inorganic Chemistry"racing page 30.) The metals appearing in the center. positions of thelong periods of a periodic table arranged in long and short periods, andespecially those which occur in the 8th to 12th positions of the longperiods (considering the alkali metals to occimy the first position andall the rare earth metals to occupy a single position), that is, the

metals 0! Group VIII, subgroup B of Groups I and H and subgroup A ofGroups VI and VII of Mendeleefs Periodic Table, are thus included in theterm heavy metal. The metals oi Group VIII, particularly those GroupVIII metals occurring in the first long period. specifically iron cobaltand nickel, are preferred heavy metals for use in polymerizationcatalysts.

We have now discovered that the time required to effect polymerizationreactions may be further decreased by using a heavy metal catalystcomprising at least two heavy metals. When the method of this inventionis employed. it is possible to complete polymerization reactions in amuch shorter time when either of the heavy metal catalysts is employedalone. Furthermore, the polymer produced by the method of this inventionexhibit excellent properties despite the short periods oi time requiredto eflect the polymerizations.

The preierred rs of practicing this invention will be shown by thefollowing specific examples which illustrate rather than limit theinventlon.

Example I A mixture of 11 parts by weight of butadiene and 9 parts ofacrylonitrlle was agitated at 30 C. in the presence of about 20 parts ofa 2% aqueous solution of a sodium alkyl naphthalene sulfonate as anemulsifying agent, .09 part of dlisopropyl dlxanthogen as a modifier,and .05 part of hydrogen peroxide as an initiator, and a heavy metalcatalyst. The catalysts employed and the times required for thepolymerisation are recorded in the following table:

:3,}? 0mm: Time 3 gqf gfz gz complctedinAO hours. M P 0.00 0: M mop"--.cmmmmmmm 30004 fi h o an ,0 00 1mm h It will be observed that thepolymerization eflected in the presence of the third catalyst wasconsiderably faster than those conducted in the presence found that themixed heavy metal catalyst gave a faster polymerization than wasobtainable by the useinthisrecipeofanyamoim-tofeitherthe cobalt or ironcompounds alone. The product obtained by coagulating and drying thelatex obtainedbythepolymerizationinthoprecenceof the mixtures of heavymetals was plastic and phate in the absence a second heavy metal couldbe easil worked on the mill. The vulcompound.

canizates prepared therefrom had excellent ten- Erample V sile strengthand elongation and had a high rewhe n 0.001 part Of Nl(NHA)2(SO4)2'8H2OW88 f and detemnm 5 substituted for the cobaltous chloride in Example luences' Example n IV, the polymerization required 16 hours, a perlod oftime considerably shorter than can be ob- A mixture or '7 parts byweight oi butadiene tallied by the use in the above recipe of nickel and3 parts of methyl acrylate was agitated at w alum in the absence ofanother heavy metal.

35 C. in the presence of about parts of a 2% Example VI aqueous solutionof myristic acid which had been 95% neutralized with sodium hydroxide,.035 part Instead the pymphwphate mplex oi hydrogen peroxide as aninitiator, .04 part of ployed in Example IV, a mixture of 0.003 part ofdiisopropyl dixanthogen as a modifier, and 8 cats. VFe2(N'I-Il):-(SOl)r24HzO and 0.025 part of serine lyst containing 0.13part of NaePzOrlOHzO, was employed as the heavy meta-l catalytic Y000025 part of cochzmo and 0007 part of tem. The polymerization wascomplete in '76 ,F flSOO The reaction m complete in hours at C. When0.0001 part of CoClz-ZHzO 27 hours The m obmned by coagulating and0.00025 part of ZnSOr'IHzO were added in and the latex m the usualmanner was addition to the temc alum and Se rlne, the time plastic andcould be easily worked on 3 m The required to complete thepolymerization was revulcanizates obtainedi'rom the polymer had goodduced 60 hours- 1 tensile strength, high elongation, and wererpar-Ewmple V" l sui l i r in of eir arly tab 8 0 use fires because th WhenExample IV was repeated with the subhys 25 stitution or 0003 part of 1e2(NH4)2(SO4)4'24H:O

Emmple p and 0.025 part or glutathione tor the pyrophos- A mixture ofparts by weight of bummene phate complex, the polymerization required 87and 3 f styrene was a c m hours at 30 C. 01 part of the presence ofabout 25 parts of a 2% aqueous 3o c so lm solution oi myristic acidwhich had been 95% neutralized with sodium hydroxide as an emulto theglutathione complex reduced the time resifying agent, 0.036 part 01'hydrogen peroxide as quired to complete the polymerization to 76 aninitiator, 0.045 part of diisopropyl dixanthogen hours.

as a modifier, and a heavy metal catalyst. The Example VIII followingtable shows the catalysts employed and A mixtur of 55 parts or butadleneand 4 5 the times required the parts or acrylonitrile was agitated at 300. in the presence of about 25 parts of a 2% aqueous 21$ Catalyst Timesolution of myristic acid which had been 85% neutralized with sodiumhydroxide, 0.06 part of v v diisopropyl dixanthogen, and 0.035 part oi!hy- 81335 1 l?( (q: :8::: drogen peroxide. When a mixture of 0.005 part8 kg f ff }xeom letelnlahoms. of Fe:(SO4)z-9HrO and 0025 part oi.sorbitol 0.05. Noam-10mmwas employed as a catalyst, the polymerizationgggg gggfgfif: 4 required 21 hours. When 0.0005 part 0! a COCla-ZHaOwere employed in addition to the It will be observed that the use of twoheavy iron, the polymerization required only 16 hours.

metal catalysts greatly accelerated the polymer- Example IX The tamed bythe When mixture of 0.005 part 01' ransom-911:0

gg g gm t gm r g fig fi: and 0.05 part 01' cholesterol was substitutedfor 11:81 rubber a marked a has the sorbitol complex in Example VIII,the polycm 1 merization required 25 holn's. Inclusion of prepared fromthe rubber were strong and elastic, 0 0005 and could be as a gem m1replmmnt or part 01 C0012 21-110 in addition to the ironmm m 5ocholesterol complex reduced the time required to Example N effect thepolymerization to 21 hours. Although the preferred method of polymeriza-A m a 7 parts of bumene and 3 parts tion is by an emulsionpolymerization as set forth or styrene was agitated at we. in thepresence in the 8mm examplesthe heavy metal f about 25 parts of a 3%aqueous solution 00 lysts herein described may be employed inpolymyristic acid which had been 95% neutralized merization inhomegeneous systems in the preswith sodium hydroxide, (L025 M f hydrogenence or absence of solvents or diluents in the peroxide, 0.045 part ordiisopropyl dixanthogen, manners W911 kmwn e Prior and a catalyst. whena mixture f 0305 part The best results are ordinarily obtained when ofransom-0x20 and 0.13 part of omp1ex40rm1ns compound is present il I.with the mixture of heavy metal compounds as mo -10m shown above. Anenhancement of catalytic aetivity is also obtained by the use 01'mixtures oi was employed as the catalyst the reaction resimple heavymetal salts in the absence of any quired 22 hours, but when 0.00025 partof complex-forming compound, Such a process,

- Cock-21100 were included in thereclpe together while not preferred, isaccordingly within the th th i on, t lymerization re uired only broadscope of our invention.

11 hours. This is a much faster polymerization The optimum amounts ineach case depend thancan be achieved in this recipe with a mixsomewhatupon the specific heavy metal and the ture of cobaltous chloride andsodium pyrophos- Sp mplex-f rm: compound employed.

The use of too great amounts of any of the heavy metal compounds willtend to retard the polymerization, copper and manganese havingparticularly pronounced tendencies to retard the polymerization whenused in excess It will ordinarily be found that the systems willtolerate larger amounts of heavy metal compounds when a complex-formingcompound is present. The optimum amount of catalyst also dependssomewhat upon the monomers undergoing polymerization.

A particularly useful heavy metal catalyst which works well under a widevariety of conditions is a mixture of from about 0.002 to 0.01% of ironin the form of a water-soluble salt, from about 0.0035 to 0.035% ofcobalt in the form of a water-soluble salt, and from about 0.1 to 1.5%of an alkali metal pyrophosphate, all based on the polymerizablematerials. The iron may be provided by adding from about 0.01 to 0.05%of Fe:(SO4) a'9H2O, the cobalt by adding from about 0.001 to 0.01% ofCOC1z'2I-IaO. The amounts of other water soluble iron and cobalt saltsrequired to make such a heavy metal catalyst can readily be calculated.Another excellent heavy metal catalyst may be obtained by substitutingnickel for the cobalt in the above combination in about the sameamounts.

The expression heavy .metal catalyst" is used herein to signify thecatalytic combination of compounds of heavy metals and complex-formingcompound, if the latter is employed. The catalysts are preferablywater-soluble, by which is meant that the whole catalytic system willdissolve in the amount of water used in the recipe. Even catalysts whichdo not completely dissolve in the water may be employed, but their useis not preferred.

The catalytic combinations of this invention may be employed in thepolymerization of any unsaturated organic compounds which are capable ofundergoing an addition polymerization to form a high molecular weightlinear polymer. Included in this class of monomers are thebutadienes-1,3 such as butadiene-1,3 (commonly termed butadiene)isoprene, 2,3-dimethyl butadiene, piperylene, and chloroprene; arylolefins such as styrene, vinyl naphthalene, and alphachlorostyrene;acrylic and alpha-substituted acrylic acids, esters, nitriles, andamides such as acrylic acid, acrylonitrile, alpha-methacrylamtrile,alpha-chloracrylonitrile, methyl acrylate, methyl methacrylate,methacrylamide; vinyl halides, esters, ethers, and ketones such asvinylidene chloride, vinyl chloride, vinyl acetate. methyl isopropenylketone, and methyl vinyl ether. Any of the above compounds all of whichcontain a group, may also be copolymerized with monomers copolymerizabletherewith. Butadiene, for instance, may be copolymerized with one ormore monomers which enter into the polymeric chains by 1,2-addition suchas acrylonitrile, styrene, methyl acrylate, etc.

As emulsifying agents whichmay be employed in emulsion polymerizationsmay be mentioned soaps such as sodium oleate, potassium palmitate, andsodium myristate, synthetic saponaceous materials including hymolalsulfates and alkaryi sulfonates such as sodium lauryl sulfate and sodiumisopropyl naphthalene sulfonate, and salts of organic bases containinglong carbon chains such as the hydrochloride ofdiethylaminoethyloleylamide, trimethylcetylammonium methyl sulfate. thehydrochloride oi oleylamidoethyldlmethylamine, and the hydrochloride ofthe diethylaminoethoxyanilide oi oleic acid. The soaps are employed inpolymerizations under basic conditions, the salts of organic bases underacid conditions, and the synthetic saponaceous materials under acid,alkaline, or neutral conditions.

The polymerization may be eflected by various known initiators ofpolymerization such as percompounds including hydrogen peroxide, benzoylperoxide, ammonium persulfate, potassium persulfate, and other peroxidesand persalts such as persulfates, perborates, percarbonates, and thelike, as well as other types of initiators such as diazoaminobenzene,sulfur dioxide, hyposulfites, bisulfltes, dipotassium diazomethanedisulionate, and triphenylmethylazobenzene. The polymerization,particularly if conducted homogeneously, may also be initiated byactinic radiation.

The plasticity and solubility of the polymers produced by homogeneouspolymerizations may be increased by including in the charge chlorinatedcompounds such as carbon tetrachloride and trichloracetic acid, while acorresponding eiiect can be obtained in emulsion polymerizations throughthe use of sulfur-containing compounds such as the dialkyl dixanthogens,the higher tetraalkyl monoand polysulfides, mercaptoalkylthiazoles, etc.

Other methods and procedures known to be useful in connection with thepolymerization of unsaturated organic compounds are within the spiritand scope of the invention as defined in the appended claims.

We claim:

l. The method which comprises polymerizing in the form of an aqueousemulsion a mixture 40 of butadiene and a monomer copolymerizabletherewith in aqueous emulsion, in the presence of catalytic amounts ofwater-soluble salts or iron and cobalt and a water-solublepyrophosphate.

2. The method of claim 1 in which acrylonitrile is employed as themonomer.

3. The method of claim 1 in which styrene is employed as the monomer.

4. The method which comprises polymerizing in the form of an aqueousemulsion a mixture of butadiene and a monomer copolymerizable therewithin aqueous emulsion, in the presence of catalytic amounts ofwater-soluble salts of iron and nickel and a water-solublepyrophosphate.

5. The method of claim 4 in which styrene is the monomer. Y

6. The method which comprises polymerizing in aqueous emulsion a mixtureof butadiene and a monomer copolymerizable therewith in aqueousemulsion, in the presence of catalytic amounts of water-soluble salts oftwo heavy metals each of which is a heavy metal occurring in Group VIIIand the first long period of the periodic table, and also in thepresence of a water-soluble pyrophosphate.

7. The method which comprises polymerizin in aqueous emulsion a mixtureof butadiene and a monomer copolymerizable therewith an aqueousemulsion, in the presence of a' catalytic amount of a water-solubleheavy metal catalyst comprising two heavy metals each of which is aheavy metal occurring in Group V111 and the first long period of theperiodic table.

8. The method which comprises polymerizing in aqueous emulsion a mixtureof butadiene and a monomer copolymerizable therewith in aque- I thisemulsion, in the presence or a water-soluble heavy metal catalystcomprising two heavy metals each of which is a heavy metal occurring inGroup VIII and the first long period of the periodic table, the amount01' the said catalyst being less than about 1% by weight based on themixture polymerized and such that. no'more than about 0.001 to .01% byweight 01' each .ot-the said heavy metals is present in the. form ofheavy metal ions. 9. The method which comprises polymerizing in aqueousemulsion an unsaturated organic compond which contains a I one-=0 groupand which undergoes in aqueous emulsion an addition polymerizationtoiorm a high molecular weight linear polymer, in the presence of a 20catalytic amount or a water-soluble heavy metal catalyst comprising twoheavy metals each of which is a heavy metal occurring in Group VIII andthe first long period 01' the periodic table.

10. The method which comprises polymerizing in aqueous emulsion anunsaturated organic compound which containsa CH C gr oup and whichundergoes in aqueous emulsion an addition polymerization to form a highmolecular weight linear polymer, in the presence of catalytic amounts ofwater-soluble salts of two heavymetals each or which is a heavy metaloccurring in Group VIII andthe first long period of'theperiodic table,and also in the presence of a water-soluble pyrophosphate.

v D. STEWART. BENJAMIN M. G. ZWICKER.

